The present invention relates to a method for reducing the migration of aldehyde compounds found in packaging materials to the contents of packages made from such packaging materials. The present invention also relates to a package made from packaging material containing aldehyde compounds, wherein the migration of the aldehyde compounds found in the packaging material to the interior of the package is reduced. The invention still further relates to an improved paperboard packaging material prepared from recycled paper stock, wherein the recycled paper stock contains aldehyde compounds and amines to react with said aldehyde compounds, thereby preventing or slowing the migration of the aldehyde compounds from the paperboard packaging material when formed into a package.
In recent years, the use of recycled materials to prepare packages has become much more prevalent than in the past. This increased recycling activity has been driven primarily by two factors: cost/economics and environmental concerns. The types of materials that are recycled include plastics, steel, and papers.
The use of recycled materials in preparing packages does cause several problems, however. One such problem is that recycled materials often contain impurities that are not found in virgin raw materials. For example, paperboard made from recycled paper stock typically contains aldehyde compounds. These aldehyde compounds are present in the recycled paper stock due to inks that are present in the original paper being recycled, and are not present in paper made from virgin stock.
These impurities in the recycled materials can, in certain instances, cause problems in the final package prepared from the recycled materials. For example, it has been found that when packages that contain food products are prepared using recycled paper stock that contains aldehyde compounds, the aldehydes can migrate from the recycled paper stock and into the package interior, where the product is stored. This migration, or transport, of the aldehyde compounds is undesirable because the aldehyde compounds impart off flavors and off odors to the food product when they come in contact with the food product.
The present invention provides a method for reducing this migration of such aldehyde compounds to the interior of the formed package. In the provided method, amine compounds are applied to the surface of the packaging material that forms the interior of the formed package. The amine compounds chemically react with aldehyde compounds that migrate through the packaging material, thereby forming a relatively chemically inert and less volatile compound. This chemical reaction slows or prevents the further migration of the aldehyde compounds to the interior of the package formed from the packaging material. The present invention further provides a package prepared from packaging materials containing aldehyde compounds, wherein the migration of the aldehyde compounds to the interior of the formed package is reduced or prevented.
The background art teaches urea-containing compositions. U.S. Pat. No. 3,293,057, issued Dec. 20, 1966, to Rumberger, claims a composition prepared by mixing together and reacting at an elevated temperature an aqueous dispersion of individual ingredients comprising starch, urea, and a polyfunctional aldehyde, wherein said starch is present in an amount of about 9% to about 95% by weight, said urea is present in an amount of about 5% to about 80% by weight, and said aldehyde is present in an amount of about 0.5% to about 20% by weight, all based on the total solids weight of said compositions, the pH of said dispersion being no greater than about 7.
The art also teaches compositions containing urea-aldehyde reaction products. U.S. Pat. No. 4,623,412, issued Nov. 18, 1986, to Bohme et al., claims a process for producing a resin impregnated linerboard for use in the production of corrugated board, wherein the surfaces of said resin impregnated linerboard have substantially no resinous material thereon. The claimed process comprises, in sequence: (i) providing an aqueous impregnating composition comprising (a) urea-aldehyde resin, (b) a catalyst, (c) a wetting agent, and (d) from 0to about 20% of a solvent, thereby providing a linerboard substrate; (ii) applying said aqueous impregnating composition to at least one surface of said linerboard substrate to form a coating thereon; (iii) applying an aqueous primer onto said coating of said impregnating composition such that said aqueous primer causes said impregnating composition to permeate said linerboard substrate to provide said linerboard substrate with a substantially polymeric core and having substantially no resinous material on the surfaces thereof; (iv) drying said impregnated linerboard under conditions for fully curing said urea-aldehyde resin to provide said linerboard with a substantially solid resinous core and having surfaces substantially free of said urea-aldehyde resin; (v) remoistening said fully cured linerboard; and (vi) passing the remoistened linerboard to a corrugator for incorporation into the corrugated board.
U.S. Pat. No. 4,377,649, issued Mar. 22, 1983, to Sweeney et al., claims a composition for use in the manufacture of cellulosic fiber materials, which comprises (a) from 1 to 50 wt % of a wax, (b) from 1 to 30 wt % of a starch, (c) from 1 to 50 wt % of a formaldehyde based resin, and (d) a liquid carrier.
U.S. Pat. No. 3,352,705, issued Nov. 14, 1967, to Moes et al., claims a method of producing a water resistant amylaceous pigment coating on paper or paperboard which comprises applying to said paper or paperboard a pigmented aqueous solution of a starch derivative, obtained by hydrolyzing starch at a temperature of between 60 and 300xc2x0 C. with an inorganic acid in the presence of urea in an amount of from 5 to 50% by weight, calculated on the basis of starch used, and less than 50% of water, calculated on the weight of the mixture, to such an extent that a 25% aqueous solution of the starch derivative has an apparent viscosity not lower than 10 centipoise at 25xc2x0 C., and reacting said starch derivative with an aldehyde reagent capable of rendering the same insoluble, said aldehyde reagent being selected from the group consisting of said aldehydes, aldehyde donors and melamine-aldehyde precondensates, and the pH during the insolubilization reaction being from about 6 to about 9.
U.S. Pat. No. 4,775,706, issued Oct. 4, 1988, to lovine et al., claims a water-resistant, alkaline curing corrugated adhesive composition comprising: (i) from about 66-35%, based on total weight of the adhesive, solids basis, of a polymer present in latex form, prepared by polymerizing a halohydrin quaternary ammonium monomer and a vinyl polymerizable monomer; (ii) from about 10-50% based on total weight of the adhesive of a starch component comprising ungelatinized starch or a mixture of ungelatinized and gelatinized starch; (iii) from about 40-80%, based on total weight of the adhesive, of water; and (iv) sufficient alkali to provide the adhesive with a pH of about 7.5 to 13.
U.S. Pat. No. 4,855,354, issued Aug. 8, 1989, to Mohler et al., claims a curable composition of matter which consists of: (a) a starch-aldehyde resin mixture, said mixture being formed by mixing said starch and said aldehyde resin; (b) a curing agent capable of reducing the pH of the composition, wherein said curing agent is present in an amount sufficient to accelerate the cure of the composition; and (c) a solvent selected from the group consisting of water, methanol, ethanol, isopropyl alcohol and mixtures thereof; wherein the ratio of aldehyde resin to starch is from 7:5 to 5:1 by weight.
U.S. Pat. No. 3,511,744, issued May 12, 1970, to Garrett, claims a method of producing sag-resistant fiberboard comprising the steps of forming fiberboard having at least two primary surfaces, each of which being located on a side of the board opposite from the other, coating at least a portion of one of said surfaces with a sag-resistant means which helps the fiberboard resist moisture and prevents expansion of the opposite surface to result in the sagging of the fiberboard, drying said fiberboard in part, then abrasively treating at least a portion of one of said surfaces other than said coated surface to at least partially stress relieve said board by removing the crust portion on the surface of the board formed by the drying of the fiberboard, whereby the fiberboard, which is abrasively treated on one side and coated with a sag-resistant means on the opposite side, will be cupped in the direction of the abrasively treated side.
The art also teaches applying a urea-containing adhesive to corrugated paperboard. U.S. Pat. No. 4,157,318, issued Jun. 5, 1979, to Sadle et al., claims an adhesive composition adapted for use as a bonding agent for corrugated paperboard upon being subjected to heat in situ. This adhesive composition contains a carrier comprising 1 part gelatinized amylaceous material, between about 3 and 5 parts water, and between about 0.5 and 4 parts urea, said carrier, in the absence of caustic, being adapted to reduce the temperature at which bonding will take place to within the range of about 140xc2x0-155xc2x0 F.
However, none of the background art teaches applying an amine-containing composition to an aldehyde-containing packaging sheet stock used to prepare a food-containing package. Nor does the art teach that the application of such amine-containing composition to such stock will act to reduce or prevent the migration of such aldehyde compounds from the stock to the interior of the food-containing package prepared from such stock. Nor does the art teach an improved aldehyde-containing packaging sheet stock used to prepare a food-containing package, wherein the improvement comprises preparing the packaging sheet stock with amine compounds contained in the packaging sheet stock, or that the inclusion of such amine compounds in such packaging sheet stock will reduce or prevent the migration of aldehyde compounds from the stock to the interior of the food-containing package prepared from such stock.
It is therefore an object of the present invention to provide a package, especially a food package, that is prepared from material containing aldehyde compounds, wherein the migration of the aldehyde compounds from the material used to make the package and into the package interior is reduced or prevented. It is also an object of the present invention to provide a method for reducing or preventing the migration, or transport, of aldehyde compounds from the material used to make a package into the package interior.
These objects are accomplished by the invention described herein.
The present invention relates to a method for reducing or preventing the migration of aldehyde compounds present in packaging material to the interior of a package formed by said packaging material, said method comprising:
(a) selecting an initial packaging sheet stock that can be used to form a package having an interior in which an aldehyde sensitive product can be contained, wherein said initial packaging sheet stock has two primary surfaces, a first surface that forms an interior wall of said package and a second surface located on an opposite side of the initial packaging sheet stock from the first surface, wherein said second surface forms an exterior wall of said formed package, and wherein said initial packaging sheet stock contains one or more aldehyde compounds that are capable of migrating from said initial packaging sheet stock to said package interior or exterior;
(b) preparing an amine-containing composition comprising an amine that chemically reacts with said aldehyde compounds to form relatively unreactive or lower volatility compounds; and
(c) applying said amine-containing composition onto said first surface of said initial packaging sheet stock, thereby forming a coated packaging material.
The present invention further relates to an improved paperboard material prepared from recycled paper that can be used to form a package having an interior in which an aldehyde sensitive product can be contained, wherein said paperboard packaging sheet stock has two primary surfaces, a first surface that acts to form an interior wall of said package, and a second surface located on an opposite side of the paperboard packaging sheet stock from the first surface, wherein said second surface forms an exterior of said package, and wherein said paperboard stock comprises an aldehyde compound selected from the group consisting of formaldehyde, isobutylaldehyde, hexanol, heptenal, and mixtures thereof, wherein the improvement comprises including in said paperboard stock an amine that chemically reacts with said aldehyde compounds to form substantially non-migrating relatively unreactive or lower volatility compounds.
The present invention still further relates to a package used for packaging aldehyde sensitive products, said package being prepared by the method comprising:
(a) selecting an initial packaging sheet stock that can be used to form a package having an interior in which an aldehyde sensitive product can be contained, wherein said initial packaging sheet stock has two primary surfaces, a first surface that forms an interior wall of said package, a second surface located on an opposite side of said initial packaging sheet stock from said first surface, wherein said second surface forms an exterior wall of said formed package, and wherein said initial packaging sheet stock contains one or more aldehyde compounds capable of migrating from said initial packaging sheet stock to said package interior or exterior;
(b) preparing an amine-containing composition comprising an amine that chemically reacts with said aldehyde compounds to form substantially non-migrating, relatively unreactive or lower volatility compounds;
(c) applying said amine-containing composition onto said first surface of said initial packaging sheet stock, thereby forming a coated packaging material;
(d) drying said coated packaging material, as necessary, to a moisture content in the range acceptable and known in the art for packaging materials; and
(e) forming said coated packaging material into a package having an interior in which an aldehyde sensitive product can be contained, wherein said package is formed in such a manner that said first surface forms said interior of said package.